#include<stdio.h>
/*
* I_4.c
*
*  Created on: May, 14, 2009
*      Author: yimingliu@fudan.edu.cn
*/

void funI_4(){
	int a,b,h;
	int s;
	printf("input a,b,h (separated by space)\n");
	scanf("%d %d %d",&a,&b,&h);
	s = (a+b)*h/2;
	printf("Size = %d\n",s);
}